Eddy-current heater for compressedgas circuit interrupters



Jan. 21, 1964 R. G. coLcLAsER, JR., ETAL 3,118,995

EDDY-CURRENT HEATER FOR COMPRESSED-GAS CIRCUIT INTERRUPTERS Filed April2o', 1961, s sheets-sheet 1 ATTORNEY Russell N. Yeckley BY W Jan. 2l,1964 R. G. cOLcLAsER, JR., ETAL 3,118,995

EDDY-CURRENT HEATER FOR COMPRESSED-GAS CIRCUU.` INTERRUPTERS Filed April2o, 1961 s sheets-sheet 2 Jan- 21, 1964 R. G. coLcLAsER, JR., ETAL3,118,995

EDDY-CURRENT HEATER FOR COMPRESSED-GAS CIRCUIT INTERRUPTERS Filed April20, 1961 5 Sheets-Shea*l 5 Fig. 5

United States Patent O 3,118,995 EDDY-CURRENT HEATER EUR CUMPRESSED- GASCHtCUlT INTERRUPTERS Robert G. Colelaser, lr., Belmont, and Russell N.Yeclrley, Murrysville, Pa., assignors to Westinghouse ElectricCorporation, East Pittsburgh, Pa., a corporation of Pennsylvania FiledApr. 2i), 1961, Ser. No. 104,355 Claims. (Cl. Zitti-148) This inventionrelates to eddy-current heaters for cornpressed-gas circuit interruptersand, more particularly, to an `eddy-current heater for maintaining thetemperature of the high-pressure gas above its liquefaction point.

A general object of the present invention is to provide an improved andeconomical compressed-gas circuit interrupter utilizing an eddy-currentheater for preventing the temperature of the high-pressure gas fromgoing below its liquefaction point.

Still a further object of the present invention is to provide animproved compressed-gas circuit interrupter of the dead-tank type inwhich the magnetic losses are deliberately diverted to bring abouteddy-current heating loss within the high-pressure tank to maintain thetemperature of the compressed-gas above its liquefaction point.

`In compressed-gas circuit interrupters, particularly of the typeemploying an extremely eilicient arc-extinguishing yand dielectric gas,such as sultur-hexaiiuoiide (SFG) gas, it is necessary to maintain thetemperature of the high-pressure gas above its liquefaction point. Adrop of temperature means la drop in the eile-otive vapor pressure, and,for effective gas-blast interruption necessarily the igas pressure of.the high-pressure reservoir must not -fall too low. It has beencustomary to utilize heaters, energized from an independent source ofsupply, to maintain the temperature of the high-pressure gas, such assulfur-hexalluoride (SFS), gas, at .a predetermined highpressure level.Accordingly, it is a fmther object of the present invention -toeliminate as far as possible such auxiliary heating supply Land toutilize eddy-current heating losses by means of closed-turn magneticstraps, or diverting the magnetic flux into the walls lof the highpressure tank to ensure that the temperature and hence the pressure ofthe high-pressure gas supply will be adequate for its intendedinterruption purposes.

Further objects and advantages will readily become apparent upon readingthe following speciiication, taken in conjunction with the drawings, inwhich:

FIGURE 1 is a `fragments-.ry side elevational View of a portion of aoompressedagas circuit interrupter embodying the principles of thepresent invention;

FIGURE 2 is a sectional end view of the compressedgas circuitinterrupter pictured in FIGURE l;

FIGURE 3 is a vertical sectional view taken longitudinally through thecompressed-gas circuit interruptor olf FIGURE 1 illustrating the contactassemblage .at `an intermediate poiint inthe opening operation;

FIGURE 4 illustrates a modified type of tank construction;

FIGURE 5 is a Vertical sectional view taken substantially along the lineV-V of the modiiied tank construction of FIGURE 4; and,

Patented Jan. 21, 1964 lCC FIGURE 6 illustrates a side elevational viewof the bridging arc-entinguishing assemblage of FlGURE 3, but showing amodified closed magnetic strap construction.

Referring to the drawings, and more particularly to FIG. 1 thereof, thereference numeral l generally designates a compressed-gas circuitinterrupter. Generally, the compressed-gas ycircuit interrupter 1'includes a longitudiallly-extending grounded tank Z having disposedadjacent its outer ends opstanding cylindrical supports 3, 4 forsupporting in a xed operative position terminal bushings 5', 6.

Disposed interiorly of the tank structure 2 and extending longitudinallythereof is an arc-extinguishing assemblage, generally designated by thereference numeral 7, and more clearly illustrated in FIGURES 3 and 6 ofthe drawings. As shown in FIGURE 3, the arc-extinguishing assemblage 7includes a high-pressure reservoir tank 8, a main blast valve 9 and aplurality of serially-related orifice-type interrupting units l0. Agenerally laddershaped movable Contact assemblage 1l, comprising a pairof longitudinal, `spaced operating rods 11a (FIG. 6), bridged bytransverse bridging members 12 and centrallysecured movable contacts 13(FIG. 3), moves as a unit, being biased in a leftward opening direction,as viewed in FIGURE 3, by an opening accelerating spring 14.

During the `closing operation, a suitable mechanism, not shown, isoperative to rotate an internally-disposed crank-arm 1S in acountenclockwise direction and move, under tensile stress, an insulatingoperating rod t6 to `force the ladder-like movable contact assemblage 1ltoward the right and effect compression of the accelerating spring la.The movable contact assemblage is latched in the fully closed-circuitposition, in which the movable contacts 13 engage relatively stationarycontacts 17, by a suitable latch mechanism associated with the operatingmechanism 18.

During the opening operation, the latching mechanism, associated withthe `operating mechanism 18, is unlatched; and the accelerating spring14 serves to bias, in a leftward opening direction, the movable Contactassemblage 1l, thereby causing a separation between the movable contacts13 and the relatively stationary contacts 17. A plurali-ty ofserially-related arcs 19 are consequently drawn. Simultaneously with theleftward opening movement of the movable Contact assemblage vl1, theblastvalve mechanism Ztl is operated to open the blast valve 9 andpermit the blasting of high-pressure gas from the high-pressurereservoir tank 3 through suitable blast tubes 21-23 toward the orilioestructures Z4 to eect extinction of the several serially-related arcs19.

Reference may be had to United States patent application led October 7,1960, Serial No. 61,284, by Robent G. Colclaser, lr., and Russell N.Yeckley and assigned to the assignee of the instant application for adetailed and minute description ot the operation of the circuitinterrupter l.

The blast valve mechanism 2li is set forth and claimed in United Statespatent application tiled January 23, 1959, Serial No. 788,668, nowUnited States Patent 3,057,983, issued October 9, 1962, to Russell N.Yeckley, Joseph Sucha and Benjamin l. Baker and Yassigned to theassignee of the instant application.

The high-pressure gas, such as sulfur-hexafluoride (SFG) gas 4d, whichis stored in the high-pressure reservoir chamber t8, -is fed thereintoby an insulating feed tube 25 which connects with an auxiliaryhigh-pressure rese Voir tank 26.

As shown more clearly in FIGS. l and 2 of the drawings, the auxiliaryhigh-pressure reservoir tank 26 comprises a semi-circular section 27 anda pair of end plates 2S, which may serve as suitable supports for thecornpressed-gas circuit interruptor l.

A non-magnetic strip 29 and welds Sti and 3l extend lengthwise of thetank structure 2, and force the magnetic circuit to pass through thewalls of the auxiliary highpressu-re tank 26 in a manner indicated bythe arrows 32.

As well known by those skilled in the art, in the closedcircuit positionof the circuit interruptor ll, relatively heavy loa-d currents passthrough the arc-extinguishing assemblage 7. This passage of current isaccompanied by an associated magnetic field, which, due to thenonmagnetic strip 2% and welds 3i), 3d, is forced to pass through thelower-disposed auxiliary high-pressure reservoir tank 26 in the mannerillustrated by the arrows 32 of FIGURE 2.

The passage of such a magnetic ux through the steel walls of theauxiliary tank 26 sets up eddy-current losses within the metallic wallsof the Itank 26, and brings about a heating effect. This is verydesirable inasmuch as at the 260 pound pressure, which the SFG gas hasattained within the tanks 8, 26, the SFS gas will liquefy at a 42 F.temperature. Heat must, therefore, be supplied When temperatures gobelow this value. It has been previously proposed that heater units beinserted into the auxiliary high-pressure reservoir tanks to meet thisproblem. In addition, insulation to provide a thermal lag in the eventof heater failure is placed around the auxiliary rese-rvoir tanks asshown in FIG. 2. Additionally, it has been proposed to provide twoheaters in each auxiliary high pressure tank energized from separatesources `for the ultimate in reliability.

The present invention is particularly concerned with a means ofutilizing eddy currents, produced in the walls of the high-pressurelreservoir tanks by the normal load currents of the breaker, to providethe necessary heating effect to prevent the SFS gas pressure fromdropping to too low values. -It is this source of heat which can be usedto increase the reliability of the interruptor 1. As illustrated inFlGURES l and 2, there is incorporated in the present invention theWalls of the high-pressure auxiliary reservoir tank 26 in the magneticcircuit of the interruptor. The high-pressure reservoir tank 2.6 isformed by the semi-circular section 27 and the two straight end plates28. The plates 28 serve as heads on the ends of the auxiliary tank 2d.Additionally, braces 35 may be used to strengthen the sides and also themain tank 2. A non-magnetic strip 29 is used in the main tank 2 to forcethe magnetic ilux into the high-pressure resenvoir tank 26. The ribs 35also act as radiator strips. An electric heater element 36 is alsoshown. This is a supplementary heat source `when the breaker is closedand may be necessary during cold weather when the breaker is open.

Associated in heat-transmitting relationship with the high potentialhigh-pressure reservoir tank S of FIGURE 3 is a closed strap 33 ofmagnetic material, such as iron or steel, to convey the heat set uptherein by eddy-current losses to the walls of the tank 8. The closedmagnetic strap 33 encircles the load current passing through theextinguishing assemblage 7 and thus has magnetic flux induced therein.This induced magnetic liux results in the establishment of eddy currentsin the strap 33 leading to 'heating thereof. This heat, in turn, istransmitted to the tank S. This assists in maintaining the temperatureof the high-pressure gas within tank d at the desired high level valueand prevents liquefaction thereof.

With reference to FIGURE 6 of the drawings, it will be noted that amodified closed magnetic strap 33a is employed. The action is the sameas in the strap 33 of FiGURE 3. Heat from the modied closed magneticstrap 33a is `transmitted to the high-pressure tank 8.

FIGURES 4 and 5 show a modified tank construction in which thehigh-pressure auxiliary tank 26a encircles the centrally disposedexhaust tank 2. Again eddy-current losses heat the 'central portion 2aof the tank 2, which constitutes the inner wall of the outer encirclingtank 26a. ln addition, there may occur some eddycurrent heating of theouter wall 34 of the modified auxiliary tank 26a.

From .the foregoing description it will be apparent that there has beendisclosed la novel utilization of eddycurrent heating losses to effectthe maintenance of the temperature of the high-pressure tank above thatof the liquefaction point. This is done by utilizing the normal loadcurrent passing through the circuit interrupter and consequently is veryeconomical.

From the foregoing description, it will also be apparent that there areutilized eddy-currents induced in the walls of the high-pressure tank 26to supply the heat necessary to prevent liquefaction of thesulfur-hexai'luoride (SP6) gas or other gas, the lione-faction of whichit is desired to prevent. The closed breaker will be supplied with heat,and the use off the auxiliary heater 36 will be kept to a minimum, thusgreatly increasing the reliability of the circuit interrupter l.

Although there have been illustrate-d and described specific structures,it is to be clearly understood that the same are merely l:for thepurpose of illustration, and that changes and modiications may readilybe made therein by those skilled in the art, without departing from thespirit and scope of the invention.

We claim as our invention:

l. The combination in a compressed-gas circuit interruptor of Kanexhaust tank, a high-pressure auxiliary tank dispose-d outside thenormal magnetic flux path of the exhaust tank and connected to theexhaust tank, an are extinguishing assemblage disposed interiorly ofsaid exhaust tank for carrying load current, the exhaust tank and thehigh-pressure auxiliary tank collectively forming a magnetic circuitwhich encircles the normal current path through lthe circuitinterruptor, and means for divert-ing magnetic liux in the exhaust tankthrough the walls of the high-pressure auxiliary reservoir tank to bringabout eddy-current heating losses to prevent liquefaction of thehigh-pressure gas.

2. The combination as set forth in claim 1, wherein the gas comprisessulfur-hexafluoride (SFG).

3. The combination in a compressed-gas circuit interrupter `of anelongated grounded generally horizontallydisposed exhaust tank, anunderslung high-pressure auxiliary tank composed of magnetic materialdisposed outside the normal magnetic flux path of the exhaust tank andconnected to the exhaust tank, an arc-extinguishing assemblage disposedinteriorly of said exhaust -t-ank for carrying load current, the exhausttank and the highpressure auxiliary tank collectively forming a magneticcircuit which encircles the normal current path through the circuitinternupter, and means including a non-magnetic strip extendinglongitudinally ot said exhaust tank for diverting magnetic ux in theexhaust tank through the =walls of the high-pressure auxiliary reservoirtank to bring about eddy-current heating losses to prevent liquefactionof the high-pressure gas.

4. A compressed-gas circuit interruptor including a metallic tank, apair of terminal bushings extending within said tank, anarc-extinguishing assemblage including separable contact means bridgingthe interior ends of said terminal bushings, said arc-extinguishingassemblage also including a high-pressure chamber, magnetic closed strapmeans surrounding the normal current path, said high-pressure chzrmowrhaving said magneiic @inscri strap References Cite in the file of thispatent means in heabtifansmiitting relationship therewith for as-FOREIGN Av/TENTS sising in maintaining he temperature of the [gas withinn. said high-pressure chamber at the desired temperature greafibmam 2mg21% level by eddy-current heating losses generated in said 5 rance amagnetic closed strap means. OTHER REFERENCES 5. The COmbirla'tOn 3S SetOrh in Claim 4, wherein The Electric Ioninai, V01. 25, March 1928, pp.133435. the hghPFeSSUTe @as COUPFSS Sulfufhexaufde The Electric Journal,Vol. 26, No. 6, June 1928, pp.

(SFS). 312-313.

1. THE COMBINATION IN A COMPRESSED-GAS CIRCUIT INTERRUPTER OF AN EXHAUSTTANK, A HIGH-PRESSURE AUXILIARY TANK DISPOSED OUTSIDE THE NORMALMAGNETIC FLUX PATH OF THE EXHAUST TANK AND CONNECTED TO THE EXHAUSTTANK, AN ARC EXTINGUISHING ASSEMBLAGE DISPOSED INTERIORLY OF SAIDEXHAUST TANK FOR CARRYING LOAD CURRENT, THE EXHAUST TANK AND THEHIGH-PRESSURE AUXILIARY TANK COLLECTIVELY FORMING A MAGNETIC CIRCUITWHICH ENCIRCLES THE NORMAL CURRENT PATH THROUGH THE CIRCUIT INTERRUPTER,AND MEANS FOR DIVERTING MAGNETIC FLUX IN THE EXHAUST TANK THROUGH THEWALLS OF THE HIGH-PRESSURE AUXILIARY RESERVOIR TANK TO BRING ABOUTEDDY-CURRENT HEATING LOSSES TO PREVENT LIQUEFACTION OF THE HIGH-PRESSUREGAS.